Armata Pharmaceuticals Highlights Positive Results from Phase 2a diSArm Study of its Staphylococcus aureus Bacteriophage Cocktail, AP-SA02, in Late-Breaking Oral Presentation at IDWeek 2025™

LOS ANGELES, Oct. 22, 2025 — Armata Pharmaceuticals, Inc. (NYSE American: ARMP) (“Armata” or the “Company”), a clinical-stage biotechnology company focused on the development of high-purity, pathogen-specific bacteriophage therapeutics for the treatment of antibiotic-resistant and difficult-to-treat bacterial infections, today highlighted positive results from its recently completed Phase 2a diSArm study of AP-SA02 as a potential treatment for complicated Staphylococcus aureus (“S. aureus“) bacteremia (SAB) in a late-breaking oral presentation at IDWeek 2025™.

The abstract, titled “A Phase 2a Randomized, Double-Blind, Controlled Trial of the Efficacy and Safety of an Intravenous (IV) Bacteriophage Cocktail (AP-SA02) vs. Placebo in Combination with Best Available Antibiotic Therapy (BAT) in Patients with Complicated Staphylococcus aureus Bacteremia,” was accepted as a late-breaking oral presentation and was presented by Dr. Loren G. Miller, M.D., M.P.H., Professor of Medicine, David Geffen School of Medicine at UCLA, Chief, Division of Infectious Diseases at Harbor-UCLA Medical Center and the Lundquist Institute.

“The results of the diSArm study confirm, for the first time in a randomized clinical trial, the efficacy of intravenous phage therapy for S. aureus bacteremia, and we are very pleased to highlight these compelling data in an oral presentation at IDWeek,” stated Dr. Miller. “The results of this rigorously designed study provide strong rationale for advancement into a Phase 3 superiority study that, if successful, would support its use in clinical practice for Staphylococcus aureus bacteremia. High-purity, phage-based therapeutics like AP-SA02 have the potential to become the new standard of care for this common, extremely severe, and often deadly infection.”

“The positive results from the diSArm study represent another significant achievement for Armata as we aim to advance AP-SA02 into a pivotal trial,” stated Dr. Deborah Birx, Chief Executive Officer of Armata. “I would like to thank Dr. Miller and the other investigators who contributed to the efficient execution of the diSArm study, and I look forward to working with many of them on a proposed pivotal study next year. I would also like to thank Dr. Vance Fowler who served as the chair of the independent blinded adjudication committee that independently confirmed safety and efficacy findings throughout the Phase 2 trial. Finally, I would like to express my gratitude to the patients who participated in this important study, and acknowledge our partners at the U.S. Department of Defense, and our significant shareholder, Innoviva, who have each provided critical support to make this early breakthrough possible.”

Data highlights

The Phase 2a study enrolled and dosed 42 patients: 29 randomized to AP-SA02 in addition to best available antibiotic therapy (BAT) and 13 to placebo (BAT alone). Methicillin-resistant S. aureus (MRSA) was the causative pathogen in approximately 38% of both groups.

Clinical response was assessed in the intent-to-treat (ITT) population at Test of Cure (TOC) on day 12 (one week post-BAT) and End of Study (EOS) four weeks after BAT completion. Safety analysis also included data from the Phase 1b portion of the trial (n = 8).

Day 12 clinical response rates were higher in the AP-SA02 group — 88% (21/24) versus 58% (7/12) in the placebo group as assessed by blinded site investigators (PI) (p = 0.047), and 83% (20/24) in the AP-SA02 group versus 58% (7/12) in the placebo group as assessed by the blinded Adjudication Committee (AC).

Non-response/relapse rates were evaluated at one week post-BAT and at EOS. No patients in the AP-SA02 group experienced non-response or relapse (0%) by either PI or AC assessment. In contrast, the placebo group showed ~25% non-response/relapse at both later timepoints by PI (p = 0.017) and 22% at one week post-BAT (p = 0.025) and 25% at EOS (p = 0.02) by AC.

Patients treated with AP-SA02 showed trends toward rapid normalization of C-reactive protein, shorter time to negative blood culture, quicker resolution of signs and symptoms at the infection site, and shorter intensive care unit and hospital utilization.

AP-SA02 was well tolerated with no serious adverse events related to the study drug. Treatment-emergent adverse events occurred in 6% (2/35) and 0% (0/15) in the AP-SA02 and placebo groups, respectively: one patient with transient liver enzyme elevation and one patient with hypersensitivity that resolved with discontinuation of vancomycin.

New findings demonstrate that defined and reproducible genomic variants present in AP-SA02 Drug Product may provide an immediate advantage by enabling rapid, strain-specific response to each patient’s S. aureus isolate. These characterized variants can expand from a minor fraction to dominance when infecting certain patient isolates in vitro, highlighting their enhanced ability to infect those strains and the importance of integrating this diversity into Armata’s phage cocktail from the outset. This inherent flexibility may be central to achieving optimal therapeutic efficacy.

Conclusions

• AP-SA02, combined with BAT, achieved a higher and earlier cure rate compared to placebo in patients with complicated SAB at day 12 as assessed by both blinded site investigators and independent adjudicators.
• No patients who received AP-SA02 demonstrated non-response or relapse at one week post-BAT or at EOS, as assessed by both blinded site investigators and the independent adjudication committee, compared with approximately 25% in the placebo group.
• AP-SA02 appears safe with clinical efficacy against both MRSA and methicillin-sensitive S. aureus (MSSA) and showed trends toward earlier resolution and shorter hospitalization, with no evidence of relapse four weeks post-therapy.
• Defined phage variants in AP-SA02 Drug Product provide an intrinsic adaptive mechanism — a flexibility that may be key to achieving effective phage therapy across diverse patient isolates.
• These results strongly support advancement into a pivotal Phase 3 trial that Armata plans to initiate in 2026, subject to review and feedback from the U.S. Food and Drug Administration (FDA). The Company is engaged with the FDA regarding a potential superiority trial design.

About IDWeek 2025™

IDWeek 2025™ is the joint annual meeting of the Infectious Diseases Society of America (IDSA), the Society for Healthcare Epidemiology of America (SHEA), the HIV Medicine Association (HIVMA), the Pediatric Infectious Diseases Society (PIDS) and the Society of Infectious Diseases Pharmacists (SIDP). With the theme “Advancing Science, Improving Care,” IDWeek features the latest science and bench-to-bedside approaches in prevention, diagnosis, treatment and epidemiology of infectious diseases. IDWeek 2025™ took place October 19–22 in Atlanta, GA. For more information, visit www.idweek.org.

About AP-SA02 and the diSArm study

Armata is developing AP-SA02, a fixed multi-phage cocktail, for the treatment of complicated bacteremia caused by Staphylococcus aureus (including MSSA and MRSA). The diSArm study (NCT05184764) was a Phase 1b/2a, multicenter, randomized, double-blind, placebo-controlled, multiple-ascending-dose study of the safety, tolerability, and efficacy of intravenous AP-SA02 in addition to BAT versus BAT alone in adults with complicated S. aureus bacteremia. The study’s completion is an important milestone in Armata’s development of AP-SA02 and supports further clinical advancement.

The Phase 1b/2a development of AP-SA02 was partially supported by a $26.2 million Department of Defense award, received through the Medical Technology Enterprise Consortium (MTEC) and managed by the Naval Medical Research Command (NMRC) – Naval Advanced Medical Development (NAMD) with funding from the Defense Health Agency and Joint Warfighter Medical Research Program.

About Armata Pharmaceuticals, Inc.

Armata is a clinical-stage biotechnology company focused on the development of high-purity, pathogen-specific bacteriophage therapeutics for the treatment of antibiotic-resistant and difficult-to-treat bacterial infections using proprietary bacteriophage-based technology. Armata is advancing a pipeline of natural and engineered phage candidates, including clinical candidates targeting Pseudomonas aeruginosa, Staphylococcus aureus, and other pathogens, and operates in-house phage-specific cGMP manufacturing to support development and potential commercialization.

Forward-Looking Statements

This communication contains “forward-looking” statements that involve risks and uncertainties that could cause actual results to differ materially from those projected. These statements include, but are not limited to, statements about clinical development plans and timelines, regulatory interactions, the potential therapeutic benefit of AP-SA02, and other expectations regarding Armata’s business and operations. Additional information about risks and uncertainties is included in Armata’s filings with the U.S. Securities and Exchange Commission, including its Annual Report on Form 10-K filed March 21, 2025.

Media Contacts

At Armata:
Pierre Kyme
310-665-2928

Investor Relations:
Joyce Allaire
LifeSci Advisors, LLC
212-915-2569

Source: Armata Pharmaceuticals, Inc.